Light emitting device providing a collimated light beam

ABSTRACT

A light emitter is disclosed herein. An embodiment of the light emitter comprises a tube, a first aperture, a second aperture, a lens, a base mechanism, and a light path. The tube has a first end and a second end. The first aperture is located proximate the tube first end and the second aperture is located proximate the tube second end. The lens is located within the tube. The base mechanism is attached to the tube first end and has a cavity formed therein. The light path extends between the cavity and the second aperture and passes through the first aperture and through the lens.

This application is a continuation of U.S. patent application, Ser. No.09/670,467 filed Sep. 26, 2000, now U.S. Pat. No. 6,752,525 which ishereby incorporated by reference for all that is disclosed therein.

BACKGROUND

Light sensors are used in many applications to detect the presence ofobjects. A light sensor typically has a light emitter that emits lightand a light receiver that receives and detects the light emitted by theemitter. The emitter and receiver are placed across a region where thedetection of objects is sought, which creates a light path between theemitter and the receiver. When an object enters the region, the objectinterrupts the light path between the emitter and the receiver, which isdetected by associated electronics. The light sensor then transmits anindication that an object is located in the region.

One use of light sensors is in an autochanger. An autochanger is a massdata storage device having a plurality of media pieces and media playerslocated therein. The media pieces are retained within the autochanger ina plurality of media holding bays. A media handling device, sometimesreferred to as a picker, transports the media pieces between the holdingbays and the media players. In order to decrease the size of theautochanger, the picker operates in close proximity to the holding baysand, thus, the media pieces. In the event a media piece becomesdislodged from its media holding bay, the picker will likely collidewith the media piece. This collision may damage the picker, the mediapiece, and other components within the autochanger. Examples ofautochangers are illustrated in U.S. Pat. No. 5,043,962 of Wagner et a.for CARTRIDGE HANDLING SYSTEM and U.S. Pat. No. 5,719,833 of Jones forAPPARATUS FOR SECURING A CARTRIDGE ENGAGING ASSEMBLY WITHIN A CARTRIDGEHANDLING SYSTEM, both of which are hereby incorporated by reference forall that is disclosed therein.

In order to assure that the media pieces have not become dislodged fromthe media holding bays, a light sensor is used to detect the presence ofmedia pieces and other obstructions in the path of the picker. A lightemitter emits a beam of light in front of the media pieces and areceiver detects the light. Accordingly, a light path is formed betweenthe emitter and the receiver and adjacent the media holding bays. In theevent that a media piece becomes dislodged, it will cross the lightpath, disrupting the light beam. This disruption is sensed by thereceiver and transmitted to a processor within the autochanger. Anindicator may be displayed to notify an operator of the problem.Additionally, the autochanger may function in a manner that prevents thepicker from traveling in the region of the dislodged media piece.

Many of the media holding bays within the autochanger are arranged incolumns and have separate light sensors associated with each column. Oneproblem encountered with using a separate light sensor with each columnis that the light beams fan out from their sources. Therefore, as thenumber of media holding bays in the columns increases, the amount thatthe light beams fan increases. The increased fanning of the light beamsincreases the sizes of each light beam associated with each column.These large light beams cause problems with cross talk betweenindividual light sensors. For example, light emitted by a first emitterassociated with a first column may be detected by a second receiverassociated with a second column. If a media piece located in the secondcolumn becomes dislodged, the second receiver may still receive lightfrom the first emitter. Accordingly, the autochanger will not detect thedislodged media piece and may drive the picker into the dislodged mediapiece.

Another problem with a fanning light beam is that the intensity of thelight beam significantly attenuates from the source. Accordingly, as thedistance between an emitter and a detector increases, the intensity oflight received by the receiver decreases. In addition, the intensity ofthe light may vary throughout the light beam. This presents problems inthe detection of the light emitted by the emitter. For example,circuitry that monitors the output of the receiver may have a thresholdwherein an output above the threshold indicates that the light beam hasnot been disrupted and an output below the threshold indicates that thelight beam has been disrupted. The reduced intensity of light in thefanned light beam requires that the threshold be set relatively low.Another problem occurs if an emitter becomes misaligned, even by arelatively small amount relative to its corresponding receiver. Themisalignment may cause the receiver to receive light from a portion ofthe light beam that has a relatively low intensity. Accordingly, theoutput of the receiver may not be greater than the threshold, which willcause a false indication that the light beam has been disrupted and thata media piece has become dislodged.

A need exists for a peripheral device that overcomes some or all ofthese problems.

SUMMARY

A light emitter is disclosed herein. An embodiment of the light emittercomprises a tube, a first aperture, a second aperture, a lens, a basemechanism, and a light path. The tube has a first end and a second end.The first aperture is located proximate the tube first end and thesecond aperture is located proximate the tube second end. The lens islocated within the tube. The base mechanism is attached to the tubefirst end and has a cavity formed therein. The light path extendsbetween the cavity and the second aperture and passes through the firstaperture and through the lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of an autochangerhaving a plurality of light sensors incorporated therein.

FIG. 2 is a top perspective view of an embodiment of a light emitterused within the autochanger of FIG. 1.

FIG. 3A is a side cut away view of the light emitter of FIG. 2.

FIG. 3B is an exploded view of a portion of the light emitter of FIG.3A.

FIG. 3C is a detailed view of an embodiment of the lens of FIG. 3A.

FIG. 3D is a detailed view of a portion of the light emitter of FIG. 3A.

FIG. 4 is a side schematic illustration of the autochanger of FIG. 1with all the media pieces properly located within their respective mediaholding bays.

FIG. 5 is a schematic illustration of the autochanger of FIG. 4 with amedia piece dislodged from its media holding bay.

DETAILED DESCRIPTION

FIGS. 1 through 5, in general, illustrate a light emitter 150 comprisinga tube 190 having a light input end 201 (sometimes referred to herein asthe input end or the first end) and a light output end 200 (sometimesreferred to herein as the output end or the second end). The tube 190has a first aperture 220 located proximate the tube input end 200 and asecond aperture 219 located proximate the tube output end 201. A lens210 is located in the tube 190. A base mechanism 192 having a cavity 198formed therein is attached to the tube input end 201. A light path 170extends between the cavity 198 and the second aperture 219 and throughthe first aperture 220 and the lens 210.

FIGS. 1 through 5 also, in general, illustrate a light sensor comprisinga light emitter 150, a light receiver 152, and a light path 169, 170.The light emitter 150 may comprise a tube 190 having an input end 201and an output end 200. A first aperture 220 is located proximate thetube input end 200 and a second aperture 219 is located proximate thetube output end 200. A lens 210 is located in the tube 190. A basemechanism 192 having a cavity 198 formed therein is attached to the tubeinput end 201. The light receiver 152 is located a distance from thelight emitter 150 and comprises at least one photodetecting element (notshown). The light path 169, 170 extends between the cavity 198 and thelight receiver 152, wherein the light path 169, 170 passes through thetube first aperture 220, through the lens 210, through the tube secondaperture 219, and to the light receiver 152.

FIGS. 1 through 5 also, in general, illustrate an autochanger 100 thatmay comprise at least one media holding bay 122. The autochanger 100 mayhave a light emitter 150 comprising a tube 190 having an input end 201and an output end 200, wherein a first aperture 220 is located proximatethe tube input end 201 and a second aperture 219 is located proximatethe tube output end 200. A lens 210 may be located in the tube 190. Abase mechanism 192 having a cavity 198 formed therein may be attached tothe tube input end 201. A light source 230 may be located in the cavity198 adjacent the first aperture 220. A light receiver 152 may also belocated in the autochanger 100. A light path 169, 170 may extend betweenthe light emitter 150 and the light receiver 152, wherein the light path169, 170 is adjacent the at least one media holding bay 122.

Having generally described the autochanger 100 and the light emitters150, they will now be described in greater detail.

Referring to FIG. 1, the light emitters 150 are described herein asbeing located within an autochanger 100. A front, schematic illustrationof a simplified autochanger 100 is shown in FIG. 1. It is to beunderstood that the autochanger 100 described herein is for illustrationpurposes only and that the light emitters 150 and other inventiveconcepts described herein are applicable to other devices, includingother autochangers. Except for the inventive concepts described herein,the autochanger 100 may, as a non-limiting example, be substantiallysimilar to an autochanger commercially available as model C-1700 fromthe Hewlett-Packard Company of Palo Alto, Calif.

The autochanger 100 may have an upper portion 110, a lower portion 112,a left portion 114, and a right portion 116. The above-describedportions define the boundaries of a surface 120 having a plurality ofmedia holding bays 122 formed therein. The media holding bays 122 may becavities appropriately sized and shaped to retain media pieces (notshown in FIG. 1) used by the autochanger 100. For example, the mediapieces may be transported between the media holding bays 122 and a mediaplayer (not shown). The media player may serve to write data to and readdata from the media pieces in a conventional manner. The media holdingbays 122 may be arranged to form a plurality of rows 130 and columns132. In the non-limiting embodiment described herein, the autochanger100 has six rows 130 and three columns 132. The columns 132 areindividually referenced as a first column 134, a second column 136, anda third column 138.

A plurality of light emitters 150 may be attached to the autochanger 100in the proximity of the lower portion 112 and below the columns 132.More specifically, one light emitter 150 may be located below eachcolumn 132. A corresponding light receiver 152 may be located above eachof the columns 132. For example, the light receivers 152 may be attachedto the autochanger 100 in the proximity of the upper portion 110. Thelight emitters 150 may be spaced a distance S1 from each other and thelight receivers 152 may each be spaced a distance S2 from each other.The distance S1 and the distance S2 may be substantially equal and may,as an example, be approximately 7.5 inches. The light emitters 150 andthe light receivers 152 may be separated by a distance D1, which may, asan example, be approximately five feet.

The light emitters 150 are referenced individually as a first lightemitter 156, a second light emitter 158, and a third light emitter 160.The light receivers 152 are referenced individually as a first lightreceiver 164, a second light receiver 166, and a third light receiver168. A plurality of light paths 169 may extend between the lightemitters 150 and the light receivers 152 and may be located adjacent thecolumns 132. More specifically, a first light path 170 may extendbetween the first light emitter 156 and the first light receiver 164 andmay be located adjacent the first column 134. A second light path 172may extend between the second light emitter 158 and the second lightreceiver 166 and may be located adjacent the second column 136. A thirdlight path 174 may extend between the third light emitter 160 and thethird light receiver 168 and may be located adjacent the third column138. As will be described in greater detail below, the light emitters150 may emit light beams 180 that follow the light paths 169. Morespecifically, the first light emitter 156 may emit a first light beam182 along the first light path 170, the second light emitter 158 mayemit a second light beam 184 along the second light path 172, and thethird light emitter 160 may emit a third light beam 186 along the thirdlight path 174.

A non-limiting example of the first light emitter 156 is illustrated inFIG. 2. The first light emitter 156 is similar to all the light emitters150, FIG. 1, and is used herein to illustrate all the light emitters150, FIG. 1. The first light emitter 156 may have a tube 190 attached toa base mechanism 192. The tube 190 may have a cavity or a hole 194extending therethrough and may be substantially cylindrical. The basemechanism 192 may have a plurality of mounting tabs 195 attachedthereto. Each of the mounting tabs 195 may have a leg 196 with aprotrusion 197 extending therefrom. The legs 196 may be flexible and,thus, may deflect upon application of a force. The protrusions 197 maybe tapered so as to facilitate their insertion into slots in aconventional manner as described below. The mounting tabs 195 may serveto attach the first light emitter 156 to the lower portion 112, FIG. 1,of the autochanger 100. As is described in greater detail below, themounting tabs 195 along with the other structures of the base mechanism192 may be arranged to form a cavity or space 198. The space 198 may beappropriately sized and shaped to accommodate a light source (not shownin FIG. 2), such as a light-emitting diode.

A side, cut away view of the first light emitter 156 is illustrated inFIGS. 3A through 3D. The tube 190 may have a light input end 201, alight output end 200, and an interior surface 202 extendingtherebetween. The light input end 201 is sometimes referred to hereinsimply as the input end 201 and the light output end 200 is sometimesreferred to herein simply as the output end 200. The interior surface202 may be relatively dark, e.g., black, so as to absorb light. Theinterior surface 202 may have a first portion 204 and a second portion206 formed therein. A junction 208, FIG. 3B, in the form of a step mayjoin the first portion 204 and the second portion 206. The first portion204 may have diameter D2, which may, as an example, be approximately7.66 millimeters with a tolerance of approximately 0.1 millimeters. Thefirst portion 204 may also have a length L1, which may, as an example,be approximately 20.90 millimeters with a tolerance of approximately 0.2millimeters. The second portion 206 may have a diameter D3, which may,as an example, be approximately 8.65 millimeters with a tolerance ofapproximately 0.1 millimeters. The second portion 206 may also have alength L2, which may, as an example, be approximately 5.0 millimeterswith a tolerance of approximately 0.1 millimeters. The junction 208,FIG. 3B, may have a height H1 which is the difference between thediameter D2 and the diameter D3. In the example illustrated above, theheight H1 is approximately 0.99 millimeters with a tolerance ofapproximately 0.1 millimeters.

A lens 210 may be located in the second portion 206 of the tube 190 andmay abut the junction 208. The lens 210 may be a symmetrical convex lenshaving a back focal length of approximately 22.5 millimeters. Referringbriefly to FIG. 3C, the lens 210 may have an edge 212, a convex surface214, and a substantially flat surface 216. The flat surface 216 mayextend around the circumference of the lens 210 and may extend adistance D4 between the edge 212 and the convex surface 214. Thedistance D4 may be appropriately sized to abut the junction 208, FIG.3B, between the first portion 204 and the second portion 206 of the tube190. For example, the distance D4 may be slightly greater than theheight H1. The lens 210 may, as an example, be of the type commerciallyavailable from U.S. Precision Lens of Cincinnati, Ohio as part number7307-00-001. It should be noted that other types of lenses may be usedwithin the tube 190 depending on the application of the light emitters150.

A first aperture 220 may be formed in the input end 201 of the tube 190.The first aperture 220 may be formed so as to limit or otherwiserestrict light that passes from the space 198 into the tube 190. Anexploded view of the first aperture 220 is illustrated in FIG. 3D. Thefirst aperture 220 may be formed into an end piece 221 of the tube 190,wherein the end piece 221 has a thickness T. The thickness T may, as anexample, be approximately 1.5 millimeters. As illustrated in FIG. 3D,the first aperture 220 may have a conical surface 222 formed between aninner edge 224 and an outer edge 226. A diameter D5 of the inner edge224 may be larger than a diameter D6 of the outer edge 226. Thecharacteristics of the first aperture 220 may be defined by thediameters D5 and D6, wherein the diameter D5 may, as an example, beapproximately 3.73 millimeters with a tolerance of approximately 0.1millimeters. The diameter D6 may, as an example, be approximately 2.00millimeters with a tolerance of approximately 0.1 millimeters.Alternatively, the characteristics of the first aperture 220 may bedefined by an angle φ formed in the first aperture 220. For example, anaxis AA may extend axially in the hole 194 and may intersect the surface222 at the angle φ. The angle φ may, as an example, be approximately35.8 degrees.

Referring again to FIG. 3A, a light source 230, e.g., a light-emittingdiode, may be located within the space 198. When the first light emitter156 is in use, the light source 230 emits light 242 that is semi-omnidirectional as shown in FIG. 3A. Only the light 244 that propagates inthe general direction of the output end 200 of the tube 190 will passthrough the first aperture 220. Most of the remaining light will beabsorbed by the end piece 221 of the tube 190 as well as components ofthe base mechanism 192. Some of the light 244 that passes through thefirst aperture 220, however, will not be directed toward the output end200. This light is referenced as light 246 and, as shown in FIG. 3A,will intersect and be absorbed by the first portion 204 of the interiorsurface 202. The light that is directed toward the output end 200 of thetube 190 is referenced herein as the incident light 248 and willintersect the lens 210. The incident light 248 is substantiallycollimated or otherwise focused by the lens 210 to yield the first lightbeam 182, which was described above with reference to the autochanger100 of FIG. 1. The first light beam 182 follows the first light path170, which may extend axially from the light source 230 and through thetube 190.

The degree to which the first light emitter 156 collimates or otherwisefocuses the first light beam 182 is dependent on the physicalcharacteristics of the first light emitter 156, including the lens 210.For example, the degree to which the first light beam 182 is collimatedmay be changed by varying the focal length of the lens 210, thediameters D2, D3 of the tube 190, the diameters D5, D6 of the firstaperture 220, and the lengths L1, L2. Referring again to FIG. 1, in theexample cited herein, the first light beam 182 is focused so as to havea radius of approximately 2.5 inches at a distance of five feet.Accordingly, an area in the vicinity of the first light receiver 164having a diameter of approximately 2.5 inches will be illuminated. Theintensity of the first light beam 182 may be substantially constantthroughout the radius if the light emitted by the first light emitter156 is substantially constant. As will be described below, the firstlight receiver 164 will detect substantially the same intensity of lightregardless of the portion of the first light beam 182 that intersectsthe first light receiver 164.

Having described the light emitters 150, the operation of theautochanger 100 with the light emitters 150 incorporated therein willnow be described.

As described above, each of the light emitters 150 has a light path 179associated therewith. Each of the light paths 179 is located adjacent acolumn 132 of media holding bays 122. The association of the light paths179 relative to the columns 132 is illustrated in greater detail by FIG.4, which is a side view of the autochanger 100. FIG. 4 illustrates aplurality of media pieces 250 located in the media holding bays 122 ofthe first column 134 which is representative of all the columns 132,FIG. 1, For illustration purposes, the media pieces 250 are shownextending from the surface 120 of the autochanger 100. It is to beunderstood, however, that the media pieces may be recessed in theautochanger 100 behind the surface 120. As illustrated in FIG. 4, thefirst light path 170 extends between the first light emitter 156 and thefirst light receiver 164. The first light emitter 156 emits the firstlight beam 182, which follows the first light path 170 to the firstlight receiver 164 and illuminates the first light receiver 164 and itssurrounding area.

The first light receiver 164 may have at least one photodetectingelement (not shown) located therein. The photodetecting element isilluminated by the first light beam 182 and outputs a signal indicativeof the illumination. For example, the photodetecting device and, thus,the first light receiver 164, may output a voltage that isrepresentative of the intensity of light it receives. A processor (notshown) may compare the output of the photodetecting element to athreshold value. If the value output from the first light receiver 164is greater than the threshold value, an indication that the first lightbeam 182 was detected by the first light receiver 164 is transmitted toa processor within the autochanger 100.

This detection of the first light beam 182 by the first light receiver164 is indicative of no obstructions blocking the first light path 170.The processor may conclude that all the media pieces 250 are properlyretained within their respective media holding bays 122. Accordingly, amedia handling device (not shown) may move along the first column 134without colliding with a media piece. It should be noted that the firstlight path 170 may be located closer to the surface 120 of theautochanger 100 than the media handling device. This will assure thatany dislodged media pieces 250 are detected before the media handlingdevice collides with them.

An example of detecting a dislodged media piece 252 is illustrated inFIG. 5. In the example illustrated in FIG. 5, the media piece 252 hasbecome dislodged from its media holding bay 254 and is extending asubstantial distance from the surface 120 of the autochanger 100. Themedia piece 252 blocks the first light path 170, which blocks the firstlight beam 182 from reaching the first light receiver 164. Theaforementioned processor identifies the lack of light at the first lightreceiver 164 as an obstruction of the first light path 170. Accordingly,the autochanger 100 prevents the media handling device from operatingalong the first column 134 to prevent it from colliding with the mediapiece 252. It should be noted that the lack of light detected by thefirst light receiver 164 is an indication that an improper object islocated adjacent the first column 134. The object described herein is,for illustration purposes, the media piece 252.

Referring again to FIG. 1, all of the light emitters 150 function insubstantially the same manner as the first light emitter 156 describedwith reference to FIGS. 4 and 5. When the autochanger 100 is in use, thelight emitters 150 each emit a light beam 180. More specifically, thefirst light emitter 156 emits a first light beam 182, the second lightemitter 158 emits a second light beam 184, and the third light emitter160 emits a third light beam 186. Each of the light beams 180 may havean angle θ associated therewith, wherein the angle θ is representativeof the amount of fanning of the light beams 180. The angle θ may, as anexample, be approximately 4.8 degrees. In the examples used herein, theangle θ results in the light beams 180 each having a radius ofapproximately 2.5 inches at the upper portion 110 of the autochanger100. The spacing S2 between the light receivers 152 should be greaterthan the radius R so that the light beams 180 only intersect theirappropriate light receivers 152. For example, if the radius R wasgreater that the spacing S2, both the first light beam 182 and thesecond light beam 184 would intersect the first light receiver 164.Accordingly, if a media piece from the first column 134 becomesdislodged, it will not be able to be detected because light willcontinue to be received by the first light receiver 164 from the secondlight beam 184.

The radius R is a function of the angle θ and, as described above, isdependent on the physical characteristics of the light emitter 150. Asdescribed above, the radius R should be small enough so that each of thelight receivers 152 only receives light from a single light beam 180.The radius R, however, should be large enough to provide formanufacturing tolerances within the autochanger 100. For example, theradius R should be large enough so that the light paths 179 do not haveto be precisely aligned between the light emitters 150 and the lightreceivers 152. A requirement for precise alignment may cause failures ifthe light emitters 150 are jarred or otherwise moved out of position,which prevents the light paths 179 from intersecting the light receivers152.

In addition to partially collimating the light beams 180, the physicalcharacteristics of the light emitters 150 provides for light beams 180that have substantially uniform intensity throughout their radii R.Therefore, the light receivers 152 receive substantially the sameintensity of light regardless of the portions of the light beams 180that intersect the light receivers 152. This substantially consistentlight intensity alleviates the need for low level comparisons of thesignals generated by the light receivers 152 to determine if the firstlight beam 182 was received. Therefore, noise inherent in the system isless likely to affect the determination as to whether light was receivedby the light receivers 152.

Having described an embodiment of the autochanger 100 incorporating thelight emitters 150, other embodiments will now be described.

Referring to FIGS. 1 and 3, in one embodiment, the light emitters 150are physically attached to the lower portion 112 of the autochanger 100.The lower portion 112 may have a plurality of slots (not shown) locatedin the proximity of each of the light emitters 150 that correspond tothe locations of the mounting tabs 195. The bases 192 of the lightemitters 150 may be pressed against the upper portion 110 so that themounting tabs 195 pass through the slots and secure the light emitters150 to the upper portion 110. More specifically, the legs 196 maydeflect slightly to allow the protrusions 197 to pass through the slots.The protrusions 197 then serve to retain the light emitters 150 againstthe lower portion 112 of the autochanger 100. This attachment of thelight emitters 150 to the lower portion 112 reduces the assembly time ofthe autochanger 100 and may allow for existing autochangers 100 to bereadily retrofit with the light emitters 150.

In another embodiment of the autochanger 100, the light emitters 150have lenses 210 that are asymmetrical. The radius of the side of theasymmetric lens facing the light source 230 is different that the radiusfacing the output end 200 of the tube 190. The asymmetrical lenses 210provide for greater flexibility with regard to focusing the light beams180.

In another embodiment of the autochanger 100, the light sources 230 emitlight having a preselected band of wavelengths. The light receivers 152may have filters placed over them that filter out light not having thepreselected band of wavelengths. This preselected band of wavelengthslessens the likelihood that other light sources will be detected by thelight receivers 152. For example, external light sources may not havethe intensity within the preselected bandwidth to be detected by thelight receivers 152 and, thus, will not interfere with the operation ofthe autochanger 100.

The autochanger 100 has been illustrated herein with the light emitters150 and the light receivers 152 located in close proximity to thesurface 120 of the autochanger 100. This close proximity is used toassure that the light paths 179 are also located in close proximity tothe surface 120 and thus, the media holding bays 122. In anotherembodiment of the autochanger 100, the light emitters 150 and the lightreceivers 152 may be located away from the surface 120. The light paths179 may be directed to the proximity of the surface 120 and, thus, themedia holding bays 122 by the use of reflective devices, such asmirrors.

It should also be noted that the light emitters 150 and the lightreceivers 152 may be located in virtually any location within theautochanger 100. For example, they may be located so that the lightbeams 180 are directed across the rows 130 of media holding bays 122.

While an illustrative and presently preferred embodiment of theinvention has been described in detail herein, it is to be understoodthat the inventive concepts may be otherwise variously embodied andemployed and that the appended claims are intended to be construed toinclude such variations except insofar as limited by the prior art.

1. A light emitter comprising: a tube having a first end and a secondend; a first aperture located proximate said tube first end; a secondaperture located proximate said tube second end; a lens located withinsaid tube; a base mechanism attached to said tube first end, said basemechanism having a cavity formed therein; and a light path extendingbetween said cavity and said second aperture, said light path passingthrough said first aperture and through said lens.
 2. The light emitterof claim 1 and further comprising a light source located within saidbase mechanism cavity, said light source being intersected by said lightpath.
 3. The light emitter of claim 1, wherein said first aperture issmaller than said second aperture.
 4. The light emitter of claim 1,wherein said first aperture is formed by a member that partiallyencloses said tube first end.
 5. The light emitter of claim 4, whereinsaid member has a first side facing said tube first end and a secondside facing away from said tube first end, wherein said first apertureis conical, the portion of said first aperture on said member first sidebeing smaller than the portion of said aperture on said member secondside.
 6. The light emitter of claim 1, wherein said lens is acollimating lens.
 7. The light emitter of claim 1, wherein said lens isa symmetrical convex lens.
 8. The light emitter of claim 1, wherein saidlens is an asymmetrical convex lens.
 9. The light emitter of claim 1,wherein said lens has a focal length associated therewith and furthercomprising a light source, wherein said light source is located at apreselected location relative to said lens focal length.
 10. The lightemitter of claim 1, wherein said tube has an inner surface, said innersurface having a first portion and a second portion, wherein thediameter of said first portion is different than the diameter of saidsecond portion, and wherein the junction of said first portion and saidsecond portion forms a step.
 11. The light emitter of claim 10, whereinsaid lens abuts said step.
 12. The light emitter of claim 10, whereinsaid lens has a lens surface and a lens edge abutting said lens surface,said lens surface having a flat circumference portion extending fromsaid lens edge, and wherein said lens flat circumference portion abutssaid step.
 13. The light emitter of claim 10, wherein said tube firstportion has a length of about 20.9 millimeters.
 14. The light emitter ofclaim 10, wherein said tube second portion has a length of about fivemillimeters.
 15. The light emitter of claim 10, wherein said diameter ofsaid tube first portion is about 7.66 millimeters.
 16. The light emitterof claim 10, wherein said diameter of said tube second portion is about8.65 millimeters.
 17. The light emitter of claim 1, wherein said lenshas a focal length of about 22.5 millimeters.
 18. A light sensorcomprising: a light emitter comprising: a tube having a first end and asecond end; a first aperture located proximate said tube first end; asecond aperture located proximate said tube second end; a lens locatedwithin said tube; a base mechanism attached to said tube first end, saidbase mechanism having a cavity formed therein; a light receiver; and alight path extending between said cavity and said receiver, wherein saidlight path passes through said tube first aperture, through said lens,and through said tube second aperture.
 19. The light sensor of claim 18,wherein said cavity has a light source located therein and wherein saidlight path intersects said light source.
 20. The light sensor of claim19, wherein said light source is adapted to emit light having apreselected band of wavelengths and wherein said light receiver isadapted to detect light having said preselected band of wavelengths. 21.The light sensor of claim 20 and further comprising a light filterlocated in said light path, said light filter being adapted to passlight having said preselected band of wavelengths.
 22. The light sensorof claim 18, wherein said first aperture is smaller than said secondaperture.
 23. The light sensor of claim 18 wherein said first apertureis formed by a member that partially encloses said tube first end. 24.The light sensor of claim 23 wherein said member has a light side facingsaid tube first end and a second side facing away from said tube firstend, wherein said first aperture is conical, the portion of said firstaperture on said member first side being smaller than the portion ofsaid first aperture on said member second side.
 25. The light sensor ofclaim 18, wherein said lens is a collimating lens.
 26. The light sensorof claim 18, wherein said lens is a symmetrical convex lens.
 27. Thelight sensor of claim 18, wherein said lens is an asymmetrical convexlens.
 28. The light sensor of claim 18, wherein said lens has a focallength associated therewith and further comprising a light sourcelocated at a preselected location relative to said lens focal length.29. The light sensor of claim 18, wherein said tube has an innersurface, said inner surface having a first portion and a second portion,wherein the diameter of said first portion is different than thediameter of said second portion, and wherein the junction of said firstportion and said second portion forms a step.
 30. The light sensor ofclaim 29, wherein said lens abuts said step.
 31. The light sensor ofclaim 29, wherein said lens has a lens surface and a lens edge abuttingsaid lens surface, said lens surface having a flat circumference portionextending from said lens edge, and wherein said lens flat circumferenceportion abuts said step.
 32. An autochanger comprising: at least onemedia holding bay; a light emitter comprising: a tube having a first endand a second end; a first aperture located proximate said tube firstend; a second aperture located proximate said tube second end; a lenslocated in said tube; a base mechanism attached to said tube first end,said base mechanism having a cavity formed therein; a light sourcelocated in said cavity adjacent said first aperture; a light receiver;and a light path extending between said light emitter and said lightreceiver, at least a portion of said light path being adjacent said atleast one media holding bay.
 33. The autochanger of claim 32, whereinsaid light source is adapted to emit light having a preselected band ofwavelengths and wherein said light receiver is adapted to detect lighthaving said preselected band of wavelengths.
 34. The autochanger ofclaim 33 and further comprising a light filter located in said lightpath, said light filter being adapted to pass light having saidpreselected band of wavelengths.
 35. The autochanger of claim 32,wherein said first aperture is smaller than said first aperture.
 36. Theautochanger of claim 32 wherein said first aperture is formed by amember that partially encloses said tube first end.
 37. The autochangerof claim 36, wherein said member has a first side facing said tube firstend and a second side facing away from said tube first end, wherein saidfirst aperture is conical, the portion of said first aperture on saidmember first side being smaller than the portion of said aperture onsaid member second side.
 38. The autochanger of claim 32, wherein saidlens is a collimating lens.
 39. The autochanger of claim 32, whereinsaid lens is a symmetrical convex lens.
 40. The autochanger of claim 32,wherein said lens is an asymmetrical convex lens.
 41. The autochanger ofclaim 32, wherein said lens has a focal length associated therewith andwherein said light source is located at a preselected location relativeto said lens focal length.
 42. The autochanger of claim 32, wherein saidtube has an inner surface, said inner surface having a first portion anda second portion, wherein the diameter of said first portion isdifferent than the diameter of said second portion, and wherein thejunction of said first portion and said second portion forms a step. 43.The autochanger of claim 42, wherein said lens abuts said step.
 44. Theautochanger of claim 42, wherein said lens has a lens surface and a lensedge abutting said lens surface, said lens surface having a flatcircumference portion extending from said lens edge, and wherein saidlens flat circumference portion abuts said step.
 45. An autochangercomprising: at least one media holding bay; means for producing asubstantially collimated light beam; and means for detecting saidsubstantially collimated light beam; and a light path associated withsaid substantially collimated light beam extending between said lightemitter and said light receiver, at least a portion of said light pathbeing adjacent said at least one media holding bay.